1. Field
The present invention relates to display modules. More particularly embodiments of the present invention relate to display module packages and system applications thereof.
2. Background Information
Light emitting diodes (LEDs) are increasingly being considered as a replacement technology for existing light sources. For example, LEDs are found in signage, traffic signals, automotive tail lights, mobile electronic displays, and televisions. Some specific mobile electronics are smart electronic devices, such as smartphones, smartwatches, etc. including more advanced computing capability than a feature phone or watch. Demand is increasing for thinner, lighter weight, and lower cost smart electronic devices, with higher resolution and larger touch screens. Organic light emitting diode (OLED) display and liquid crystal display (LCD) are the two most widely adopted display technologies in current smart electronic devices.
OLED technology generally includes a layer of an organic compound in a pixel area, and a thin film transistor (TFT) backplane to switch each individual pixel on or off. An OLED display works without a backlight and can display deep black levels. The organic compound layer is sensitive to air and moisture, which can lead to degradation of the display. OLED displays are typically encapsulated with a rigid glass cover to protect the organic compound from air and moisture.
LCD technology generally includes pixels filled with liquid crystals, and a thin film transistor (TFT) backplane to switch each individual pixel on or off. Since the liquid crystals do not produce light by themselves, they need backlight illumination from behind or side of the display panel.
Two widely adopted manners for packaging display modules based on OLED or LCD include chip-on-glass (COG) packaging and chip-on-film (COF) packaging. FIGS. 1A-1B are exemplary schematic cross-sectional side view and schematic front view illustrations of a COG packaged display module. As illustrated, the display module 100 includes a display panel 115 connected to a printed circuit board (PCB) 106 by a flexible printed circuit (FPC) 108. The display panel 115 includes a display substrate 102 formed of either OLED or LCD display technologies, one or more driver ICs 110 mounted on the display substrate 102 and a cover 114 over the display substrate. A seal ring 113 may surround the display area 101 of the display substrate for attaching the cover 114 and sealing the display area 101 from air and moisture. In smart electronic devices the display substrate 102 may additionally include a touch screen within the display area 101. Alternatively a touch screen can be formed over the display substrate 102. In the case of LCD display technology, a backlight 105 is located behind the display substrate.
Additional devices and IC chips 104 for operating the display module 100 are located off of the display substrate 102 on PCB 106. For example, IC chips 104 can include a power management IC, processor, timing controller, touch sense IC, wireless controller, communications IC, etc. As illustrated, the PCB 106 is connected to the display substrate 102 with FPC 108, with contact areas 107 of the FPC 108 bonded to surfaces of the display substrate 102 and PCB 106. Referring to both FIGS. 1A-1B, the area reserved on the display substrate for the one or more driver ICs 110 and contact area 107 are referred to as a contact ledge 111. The PCB 106 may extend laterally from the display substrate 102, or alternatively can be wrapped behind the display substrate as illustrated. As shown in FIGS. 1A-1B, a lateral extension length 109 of the FPC 108 may be associated with the FPC 108 of the display module, even where the PCB 106 is wrapped behind the display substrate 102. A battery 112 may also be located behind the display substrate with the PCB 106.
COF packaging is similar to COG packaging, with one main difference being that the one or more driving ICs 110 are moved from the display substrate 102 onto the FPC 108. In such applications, the contact ledge may require less space than COG packaging.